/* ------------------------- readjpeg.c ------------------------- */
/* (C) Thomas Merz 1994-2002 */

#include <stdio.h>
#include <string.h>

/* try to identify Mac compilers */
#ifdef __MWERKS__
#if __POWERPC__ || __CFM68K__ || __MC68K_
#define MAC
#else
#define DOS
#endif
#endif /* __MWERKS__ */

#ifndef DOS
#include <unistd.h>
#endif

#include "psimage.h"

/* The following enum is stolen from the IJG JPEG library
 * Comments added by tm
 * This table contains far too many names since jpeg2ps
 * is rather simple-minded about markers
 */

extern BOOL quiet;

typedef enum
{                /* JPEG marker codes			*/
  M_SOF0 = 0xc0, /* baseline DCT				*/
  M_SOF1 = 0xc1, /* extended sequential DCT		*/
  M_SOF2 = 0xc2, /* progressive DCT			*/
  M_SOF3 = 0xc3, /* lossless (sequential)		*/

  M_SOF5 = 0xc5, /* differential sequential DCT		*/
  M_SOF6 = 0xc6, /* differential progressive DCT		*/
  M_SOF7 = 0xc7, /* differential lossless		*/

  M_JPG = 0xc8,   /* JPEG extensions			*/
  M_SOF9 = 0xc9,  /* extended sequential DCT		*/
  M_SOF10 = 0xca, /* progressive DCT			*/
  M_SOF11 = 0xcb, /* lossless (sequential)		*/

  M_SOF13 = 0xcd, /* differential sequential DCT		*/
  M_SOF14 = 0xce, /* differential progressive DCT		*/
  M_SOF15 = 0xcf, /* differential lossless		*/

  M_DHT = 0xc4, /* define Huffman tables		*/

  M_DAC = 0xcc, /* define arithmetic conditioning table	*/

  M_RST0 = 0xd0, /* restart				*/
  M_RST1 = 0xd1, /* restart				*/
  M_RST2 = 0xd2, /* restart				*/
  M_RST3 = 0xd3, /* restart				*/
  M_RST4 = 0xd4, /* restart				*/
  M_RST5 = 0xd5, /* restart				*/
  M_RST6 = 0xd6, /* restart				*/
  M_RST7 = 0xd7, /* restart				*/

  M_SOI = 0xd8, /* start of image			*/
  M_EOI = 0xd9, /* end of image				*/
  M_SOS = 0xda, /* start of scan			*/
  M_DQT = 0xdb, /* define quantization tables		*/
  M_DNL = 0xdc, /* define number of lines		*/
  M_DRI = 0xdd, /* define restart interval		*/
  M_DHP = 0xde, /* define hierarchical progression	*/
  M_EXP = 0xdf, /* expand reference image(s)		*/

  M_APP0 = 0xe0,  /* application marker, used for JFIF	*/
  M_APP1 = 0xe1,  /* application marker			*/
  M_APP2 = 0xe2,  /* application marker			*/
  M_APP3 = 0xe3,  /* application marker			*/
  M_APP4 = 0xe4,  /* application marker			*/
  M_APP5 = 0xe5,  /* application marker			*/
  M_APP6 = 0xe6,  /* application marker			*/
  M_APP7 = 0xe7,  /* application marker			*/
  M_APP8 = 0xe8,  /* application marker			*/
  M_APP9 = 0xe9,  /* application marker			*/
  M_APP10 = 0xea, /* application marker			*/
  M_APP11 = 0xeb, /* application marker			*/
  M_APP12 = 0xec, /* application marker			*/
  M_APP13 = 0xed, /* application marker			*/
  M_APP14 = 0xee, /* application marker, used by Adobe	*/
  M_APP15 = 0xef, /* application marker			*/

  M_JPG0 = 0xf0,  /* reserved for JPEG extensions		*/
  M_JPG13 = 0xfd, /* reserved for JPEG extensions		*/
  M_COM = 0xfe,   /* comment				*/

  M_TEM = 0x01, /* temporary use			*/

  M_ERROR = 0x100 /* dummy marker, internal use only	*/
} JPEG_MARKER;

/*
 * The following routine used to be a macro in its first incarnation:
 *  #define get_2bytes(fp) ((unsigned int) (getc(fp) << 8) + getc(fp))
 * However, this is bad programming since C doesn't guarantee
 * the evaluation order of the getc() calls! As suggested by
 * Murphy's law, there are indeed compilers which produce the wrong
 * order of the getc() calls, e.g. the Metrowerks C compilers for BeOS
 * and Macintosh.
 * Since there are only few calls we don't care about the performance
 * penalty and use a simplistic C function.
 */

/* read two byte parameter, MSB first */
static unsigned int get_2bytes(FILE *fp)
{
  unsigned int val;
  val = (unsigned int)(getc(fp) << 8);
  val += (unsigned int)(getc(fp));
  return val;
}

static int next_marker(FILE *fp)
{ /* look for next JPEG Marker  */
  int c, nbytes = 0;

  if (feof(fp)) return M_ERROR; /* dummy marker               */

  do
    {
      do
        { /* skip to FF 		  */
          nbytes++;
          c = getc(fp);
        }
      while (c != 0xFF);
      do
        { /* skip repeated FFs  	  */
          c = getc(fp);
        }
      while (c == 0xFF);
    }
  while (c == 0); /* repeat if FF/00 	      	  */

  return c;
}

/* analyze JPEG marker */
BOOL AnalyzeJPEG(imagedata *image)
{
  int b, c, unit;
  unsigned long i, length = 0;
#define APP_MAX 255
  unsigned char appstring[APP_MAX];
  BOOL SOF_done = FALSE;

  /* Tommy's special trick for Macintosh JPEGs: simply skip some  */
  /* hundred bytes at the beginning of the file!		  */
  do
    {
      do
        { /* skip if not FF 		  */
          c = getc(image->fp);
        }
      while (!feof(image->fp) && c != 0xFF);

      do
        { /* skip repeated FFs 	  */
          c = getc(image->fp);
        }
      while (c == 0xFF);

      /* remember start position */
      if ((image->startpos = ftell(image->fp)) < 0L)
        {
          fprintf(stderr, "Error: internal error in ftell()!\n");
          return FALSE;
        }
      image->startpos -= 2; /* subtract marker length     */

      if (c == M_SOI)
        {
          fseek(image->fp, image->startpos, SEEK_SET);
          break;
        }
    }
  while (!feof(image->fp));

  if (feof(image->fp))
    {
      fprintf(stderr, "Error: SOI marker not found!\n");
      return FALSE;
    }

  if (image->startpos > 0L && !quiet)
    {
      fprintf(stderr, "Note: skipped %ld bytes ", image->startpos);
      fprintf(stderr, "Probably Macintosh JPEG file?\n");
    }

  /* process JPEG markers */
  while (!SOF_done && (c = next_marker(image->fp)) != M_EOI)
    {
      switch (c)
        {
        case M_ERROR:
          fprintf(stderr, "Error: unexpected end of JPEG file!\n");
          return FALSE;

        /* The following are not officially supported in PostScript level 2 */
        case M_SOF2:
        case M_SOF3:
        case M_SOF5:
        case M_SOF6:
        case M_SOF7:
        case M_SOF9:
        case M_SOF10:
        case M_SOF11:
        case M_SOF13:
        case M_SOF14:
        case M_SOF15:
          fprintf(stderr, "Warning: JPEG file uses compression method %X - proceeding anyway.\n", c);
          fprintf(stderr, "PostScript output does not work on all PS interpreters!\n");
          /* FALLTHROUGH */

        case M_SOF0:
        case M_SOF1:
          length = get_2bytes(image->fp); /* read segment length  */

          image->bits_per_component = getc(image->fp);
          image->height = (int)get_2bytes(image->fp);
          image->width = (int)get_2bytes(image->fp);
          image->components = getc(image->fp);

          SOF_done = TRUE;
          break;

        case M_APP0: /* check for JFIF marker with resolution */
          length = get_2bytes(image->fp);

          for (i = 0; i < length - 2; i++)
            { /* get contents of marker */
              b = getc(image->fp);
              if (i < APP_MAX) /* store marker in appstring */
                appstring[i] = (unsigned char)b;
            }

            /* Check for JFIF application marker and read density values
             * per JFIF spec version 1.02.
             * We only check X resolution, assuming X and Y resolution are equal.
             * Use values only if resolution not preset by user or to be ignored.
             */

#define ASPECT_RATIO 0  /* JFIF unit byte: aspect ratio only */
#define DOTS_PER_INCH 1 /* JFIF unit byte: dots per inch     */
#define DOTS_PER_CM 2   /* JFIF unit byte: dots per cm       */

          if (image->dpi == DPI_USE_FILE && length >= 14 && !strncmp((const char *)appstring, "JFIF", 4))
            {
              unit = appstring[7]; /* resolution unit */
                                   /* resolution value */
              image->dpi = (float)((appstring[8] << 8) + appstring[9]);

              if (image->dpi == 0.0)
                {
                  image->dpi = DPI_USE_FILE;
                  break;
                }

              switch (unit)
                {
                /* tell the caller we didn't find a resolution value */
                case ASPECT_RATIO:
                  image->dpi = DPI_USE_FILE;
                  break;

                case DOTS_PER_INCH:
                  break;

                case DOTS_PER_CM:
                  image->dpi *= (float)2.54;
                  break;

                default: /* unknown ==> ignore */
                  fprintf(stderr, "Warning: JPEG file contains unknown JFIF resolution unit - ignored!\n");
                  image->dpi = DPI_IGNORE;
                  break;
                }
            }
          break;

        case M_APP14: /* check for Adobe marker */
          length = get_2bytes(image->fp);

          for (i = 0; i < length - 2; i++)
            { /* get contents of marker */
              b = getc(image->fp);
              if (i < APP_MAX) /* store marker in appstring */
                appstring[i] = (unsigned char)b;
            }

          /* Check for Adobe application marker. It is known (per Adobe's TN5116)
           * to contain the string "Adobe" at the start of the APP14 marker.
           */
          if (length >= 12 && !strncmp((const char *)appstring, "Adobe", 5)) image->adobe = TRUE; /* set Adobe flag */

          break;

        case M_SOI: /* ignore markers without parameters */
        case M_EOI:
        case M_TEM:
        case M_RST0:
        case M_RST1:
        case M_RST2:
        case M_RST3:
        case M_RST4:
        case M_RST5:
        case M_RST6:
        case M_RST7:
          break;

        default: /* skip variable length markers */
          length = get_2bytes(image->fp);
          for (length -= 2; length > 0; length--) (void)getc(image->fp);
          break;
        }
    }

  /* do some sanity checks with the parameters */
  if (image->height <= 0 || image->width <= 0 || image->components <= 0)
    {
      fprintf(stderr, "Error: DNL marker not supported in PostScript Level 2!\n");
      return FALSE;
    }

  /* some broken JPEG files have this but they print anyway... */
  if (length != (unsigned int)(image->components * 3 + 8))
    fprintf(stderr, "Warning: SOF marker has incorrect length - ignored!\n");

  if (image->bits_per_component != 8)
    {
      fprintf(stderr, "Error: %d bits per color component ", image->bits_per_component);
      fprintf(stderr, "not supported in PostScript level 2!\n");
      return FALSE;
    }

  if (image->components != 1 && image->components != 3 && image->components != 4)
    {
      fprintf(stderr, "Error: unknown color space (%d components)!\n", image->components);
      return FALSE;
    }

  return TRUE;
}
